With the advent of the Internet has come the opportunity for the print media industry to publish “on-line” rather than producing and distributing traditional paper based publications. On-line publishing has a number of advantages. From the consumer's point of view, information is available on demand, information can be navigated via hypertext links, information can be searched, and information can be automatically personalized. From the publisher's point of view, the costs of printing and physical distribution are eliminated and the publication becomes more attractive to advertisers as it can be targeted to specific demographics and linked to product sites.
On-line publication also has disadvantages. Computer screens are inferior to paper. At the same quality as a magazine page, a SVGA computer screen displays only about a fifth as much information. Both CRT's (Cathode Ray Tubes) and LCD's (Liquid Crystal Displays) have brightness and contrast problems, particularly, when ambient light is strong. Ink on paper, being reflective rather than emissive is both bright and sharp in ambient light. Accordingly, people have a natural preference to read newspapers, magazines, catalogues, brochures and other publications in a bound paper based format.
Printers that incorporate a binding means may be connected to the Internet for the on-line publication of the bound documents. However, if the paper based document is to be interactive in the same manner as a Web page, then the page will need to carry information in a form that can be read by an optical reader linked to the network. If this information is printed in a colorant that is visible to the human eye, then it is likely to obscure text or images printed on the page. Accordingly, the information to be read by the optical reader is printed in a colorant that is invisible to the human eye but visible to the optical reader device used.
The invisible colorant is an additional consumable that must be supplied to the printer. This adds to the number of interruptions to printer operation because of the need to periodically replenish each of the consumable materials as they deplete.